Soil bacterium enhances brain’s ability to learn

Researchers from The Sage Colleges in New York say that the bacterium Mycobacterium vaccae, already believed to have antidepressant qualities, could also improve the brain’s ability to learn new tasks. The findings were presented yesterday at the 110th General Meeting of the American Society for Microbiology in San Diego.

“Mycobacterium vaccae is a natural soil bacterium which people likely ingest or breath in when they spend time in nature,” says Sage’s Dorothy Matthews. Previous researchinto M. vaccae showed that heat-killed bacteria injected into mice stimulated the growth of some neurons in the brain that resulted in increased levels of serotonin and decreased anxiety.

Serotonin also plays a role in learning so Matthews and co-researcher Susan Jenks fed live bacteria to laboratory mice and assessed their ability to navigate a maze compared to control mice that were not fed the bacteria. “We found that mice that were fed live M. vaccae navigated the maze twice as fast and with less demonstrated anxiety behaviors as control mice,” said Matthews.

In another experiment, the bacteria were removed from the diet of the experimental mice and they were retested. While the mice ran the maze slower than they did when they were ingesting the bacteria; on average they were still faster than the control mice.

A final test was given to the mice after three weeks’ rest. While the experimental mice continued to navigate the maze faster than the controls, the results were no longer statistically significant, suggesting the effect of the bacterium is temporary.

“This research suggests that M. vaccae may play a role in anxiety and learning in mammals,” says Matthews. “It is interesting to speculate that creating learning environments in schools that include time in the outdoors where M. vaccae is present may decrease anxiety and improve the ability to learn.”